The primary objective of the Clinical Core (Core B) will be to provide a well-characterized cohort of subjects with autism and autism spectrum disorders and non-autistic control subjects for enrollment in GNYARCE research projects and collaborative endeavors. Core B will acquire comprehensive clinical and laboratory data through diagnostic evaluation and assessment of comorbidity, cognitive, developmental, and adaptive assessment, medical history and screening, and genetic sample collection from autistic and autism spectrum subjects as well as family members and control/comparison subjects, as appropriate. It will collect a common set of assessment data and measure target core symptom domains and associated features and comorbid conditions to better define the cohort. The Core will provide baseline evaluation to assess diagnostic eligibility and cognitive ability, perform a functional analysis, and characterize core symptomatology for inclusion in Projects I, II, and III. To accomplish its goals, Core B will utilize three clinical research sites and a genetic research site: the Seaver Autism Research Center at the Mount Sinai School of Medicine, the Cody Center for Autism and Developmental Disabilities at the State University of New York at Stony Brook, the Center for Autism in the North Shore-Long Island Jewish Health System, and the Family Genetic Studies Program at Mount Sinai.